This invention relates to electronics, in general, and to transmitters having modulation circuitry and methods of operation, in particular.
Cellular telephones operate under a wide variety of wireless protocols. Examples of such wireless protocols include a digital cellular service (DCS) wireless protocol, a global system for mobile telephones (GSM) wireless protocol, and an enhanced GSM (EGSM) wireless protocol. Other examples of such wireless protocols include a time division multiple access (IS-136 TDMA) wireless protocol and its precursor North American digital cellular (NADC) wireless protocol. Still further examples of such wireless protocols include a RAM Mobile Data wireless protocol, an integrated digitally enhanced network (IDEN) wireless protocol, and an advanced mobile phone service (AMPS) wireless protocol. Many of the wireless protocols require a unique transmission modulation mode or technique.
In the past, cellular telephones operated under a single wireless protocol, but new cellular telephones are capable of operating under two wireless protocols. An example is a cellular telephone that operates primarily on a GSM system using the GSM wireless protocol, but can roam outside the GSM system and register on a TDMA system using the IS-136 TDMA wireless protocol. However, these new cellular telephones use extremely inefficient and costly circuitry to support the diverse requirements of the multiple modulation modes for the different wireless protocols. The circuitry used in single modulation cellular telephones is often reused in multiple mode cellular telephones in a parallel manner. However, this mere aggregation of old circuitry produces a high parts count and complex programming in the new cellular telephones.
Accordingly, a need exists for a transmitter and method of operation that efficiently and cost-effectively supports the diverse requirements of the multiple modulation modes required for the different wireless protocols. Furthermore, a need exists for a transmitter and method of operation to be capable of operating under at least a majority of the wireless protocols in a single cellular telephone.